The randomized, phase 2 trial was conducted at 11 sites across the United States and is the latest to demonstrate the psychedelic drug’s potential as a treatment for depression.
The project was funded by Usona Institute, a nonprofit medical research organization based in Madison, Wisc. The institute issued a press statement, but researchers did not comment further on the findings.
“As the largest and most rigorous study conducted across a wide spectrum of individuals with major depressive disorder, the results show promise for all people struggling with this condition,” lead author Charles Raison, MD, director of clinical and translational research at Usona, said in the statement.
The 34 coauthors on the study are affiliated with public universities, research centers, and private companies. Eight of the investigators are identified as employees of Usona Institute.
Declining further comment, an institute spokesperson told this news organization that, “Usona has chosen the approach of no interviews, and this applies for all coauthors.”
The findings were published online in JAMA.
Largest study to date
Usona’s investigational psilocybin drug has been granted a breakthrough designation by the Food and Drug Administration, a process designed to speed drug development and review.
Previous smaller studies have suggested a rapid antidepressant response with psilocybin, but they have been small, unblinded, and have had short duration of follow-up, they write. This randomized, double-blind, phase 2 clinical trial is the largest study of psilocybin for depression to date, the researchers note.
It included 104 adults aged 21-65 years with MDD who had a current depressive episode of at least 60 days and a Montgomery-Åsberg Depression Rating Scale (MADRS) total score of 28 or more at baseline.
Participants had to be free of psychedelic drugs for at least 5 years, have had no active suicidal ideation or suicidal behavior in the prior 12 months, no personal or first-degree family history of psychosis or mania, and no history of moderate/severe alcohol or drug use disorder.
Before the study, participants had a 7- to 35-day screening period for psychiatric medication tapering, underwent baseline assessments, and received 6-8 hours of preparation with two facilitators who would be with them during dosing.
Dosing occurred within 7 days of baseline assessments. During the 6- to 8-hour session, participants received either a single 25-mg oral dose of psilocybin or 100-mg dose of niacin. One participant randomly assigned to receive psilocybin received the incorrect treatment, resulting in 50 participants receiving psilocybin and 54 receiving niacin.
Participants returned the next day, the next week, and then every 2 weeks for assessments, for a follow-up of 6 weeks.
Participants who received psilocybin reported significantly greater improvements in MDD symptoms, compared with those who received niacin. MADRS scores – a scale from 0 to 60 where higher scores indicate more severe depression – showed greater reductions with treatment vs. placebo at 8 days (mean difference, −12.0; 95% confidence interval, −16.6 to −7.4; P < .001), and at day 43 (mean difference, −12.3; 95% CI, −17.5 to −7.2; P < .001).
More participants receiving psilocybin had sustained depressive symptom response (42% vs. 11%; P = .002) and more improvement in the Sheehan Disability Scale score, which measures functional disability, 43 days after treatment (P < .001).
The effects persisted through the end of the study, although the differences between groups were no longer significant by week 6.
“This is another exciting piece of evidence that adds to the current literature regarding the potential efficacy of psilocybin for the treatment of mental health conditions, particularly depression,” said Greg Fonzo, MD, codirector of the Center for Psychedelic Research and Therapy at the University of Texas at Austin, who commented on the findings.
Significantly more people in the psilocybin group reported at least one treatment-related adverse event (AE, 82% vs. 44%), although most were mild to moderate. Headache and nausea were the most common side effects and most resolved within 1 day of dosing.
While those numbers are high, Dr. Fonzo said they’re not out of line with AEs reported in other studies.
“Particularly with the types of adverse events reported here, like headache and nausea, those are things you would typically expect to see in this treatment,” said Dr. Fonzo, who was not part of the research.
“But it is high, and it underscores that this is not a treatment without certain risks, even though it was good that they were primarily mild in severity,” he added.
A ‘stepping stone’ to FDA approval?
The use of tools to measure disability in addition to symptoms of depression severity is a strength of the study, Dr. Fonzo added. The use of an active comparator and the 6-week follow-up also offer something new over previous studies.
Despite the longer follow up, questions remain about the durability of response, something only a longer study could answer, Dr. Fonzo said. The small and homogeneous sample-size are also a concern. Nearly 90% of participants were White, and more than half had an income of $75,000 a year or higher.
“It’s another stepping stone in the process to FDA approval, but the next step in that process would be much larger phase 3 trials that would have much larger samples, a longer follow-up, and hopefully have a more inclusive swath of the population,” Dr. Fonzo said.
But perhaps one of the most significant limitations is the use of niacin as an active comparator, said Caleb Alexander, MD, codirector of the Center for Drug Safety and Effectiveness at Johns Hopkins University in Baltimore.
The use of an agent that doesn’t produce effects similar to those expected from a psychedelic introduced the potential for functional unblinding, Dr. Alexander said. Investigators did not ask participants to guess whether they received psilocybin or niacin, so the quality of the blinding was not assessed in the study.
“We’d like to see the use of [an] active comparator that might have a chance of obscuring to people as to whether they’ve been randomized to the treatment arm or control arm,” said Dr. Alexander, who wasn’t involved in the study. “Why not use a benzodiazepine or another drug that produces a transient euphoria that would better obscure whether or not people were receiving the psilocybin?”
The authors of an accompanying editorial shared these concerns, also noting that the study included “a significant number of patients who did not respond to therapy.”
“It is important to analyze and understand adverse outcomes in psychedelic trials and conduct longitudinal studies to determine how sustained the effects will be and what may initiate a recrudescence of symptoms,” write Rachel Yehuda, PhD, and Amy Lehrner, PhD, both of the Peters VA Medical Center and Icahn School of Medicine at Mount Sinai, New York.
“Future studies will help identify who is most likely to benefit from psychedelics, whether booster or repeated treatment is safe and beneficial, and what the optimal dose and therapeutic frameworks are.”
A long-term follow-up of the current trial was terminated last year because of low enrollment. The spokesperson with Usona Institute did not respond to questions about that study, and the institute’s statement only added that preparations are underway to launch another study that “will provide additional safety and efficacy data to support submission of a new drug application to the FDA.”
Usona published its manufacturing process that it used to synthesize psilocybin in an open-access journal and signed a statement on “open science and open praxis” with psilocybin and similar substances, which appears on their website. That statement was signed by 31 research and service organizations around the world and nearly 150 scientists, scholars, and practitioners.
The study was funded by Usona Institute. Dr. Raison reported receiving personal fees from Usona Institute and grants to Usona Institute from Dr. Bronner’s All-One, Fournier Family Foundation, Good Ventures, Steven and Alexandra Cohen Foundation, Tiny Blue Dot Foundation, Turnbull Family Foundation, and William A. Linton during the conduct of the study; and personal fees from Novartis, Sage/Biogen, Emory Healthcare, and Vail Health outside the submitted work. Dr. Fonzo and Dr. Alexander report no relevant financial relationships. Dr. Yehuda reports receiving nonfinancial support from the Multidisciplinary Association for Psychedelic Studies Public Benefit (MAPS PBC) and grants from COMPASS Pathways. Dr. Lehrner is an investigator on trials sponsored by MAPS PBC and COMPASS Pathways.
A version of this article first appeared on.